Swept volume

In an internal combustion engine, the informal term capacity usually refers to the Swept volume of the pistons. This can be calculated by multiplying the piston area by the stroke - that is, the difference between the top and bottom positions of the piston -, by the number of cylinders.

In most parts of the world, an engine's swept volume is given in litres, though in the USA, cubic inches are still widely used.

The compression ratio of an engine can be determined by dividing the swept volume by the total volume of the combustion chambers when the piston is at top dead centre (TDC).